Quote:
Originally Posted by DannoXYZ
Compression should be done with all plugs out. Little change with oil shows rings are fine. Problem is with valve-sealing. Might be fried exhaust valves from lack of maintenance previously.
Boots between airbox and carbs won't affect vacuum levels because it's before throttle-plates. It's restriction of throttle-plates that generates vacuum between throttle and intake-valves when pistons are on intake-stroke.
Did you verify alignment marks on cam-sprockets and that lobes point in proper direction at TDC?
More measurements needed:
1. battery voltage with everything OFF, volts = ??
2. battery voltage during cranking, volts = ?? too low of voltage will kill sparks
3. key ON, kill=RUN, voltage at coils' red terminals, volts1,2=??
4. verify spark. Remove plug-wires & plugs. Insert plugs into wires and ground case of plugs to bare metal on engine. Crank. Do you seen bright blue spark?
5. Now that you have some vacuum, re-measure petcock flow-rate to see if that amount is sufficient to fill carbs. Disconnect fuel hose from fuel-rail and aim into measuring cup. Crank for 10-sec. How much petrol did you collect? cc=???
Extremely difficult when there's little vacuum and low flow to get fuel into carbs if it has to flow uphill. Once things are moving, it's fine. But if you can't even get it moving, nothing's gonna come out. It's like syphoning petrol out of auto's tank. Have to overcome that uphill section by applying external forces. But there's no petrol pump on this bike to get past that any uphill leg of journey. Downhill or horizontal only.
6. isolate tank, petcock and carbs from fuel-delivery. Use squirt-bottle to spray 2-3cc petrol into airbox. Wait 15-sec for it to vapourise. Crank engine. Does it start & run?
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Thanks for all of your help! I'm glad that it seems like we're getting closer to the root of the problem
Here is a partial set of results.
1. Voltage with everything off: 13.37, 13.36, 13.36 (fully charged); after cranking, this resting voltage dropped to 12.5 and 12.47
2. Voltage while cranking: 11.5, 11.6, max = 11.64
3. Can you clarify what you mean by this, please? Does this mean I should get the voltage from just one terminal of the battery? If so, where do I place the other lead to close the circuit? Where do I find the coils' red terminal?
4. There is a bright white/blue spark on both spark plugs while cranking and grounding the plugs to the engine. Very consistent results/spark.
5. TBD - going to get a beaker first. Also...
6. Before putting the fuel tank back on for #5, can you clarify this test, please? What am I isolating from one another? In other words, what should I be leaving on the bike/connected vs. what should be taken off? Is the "fuel-delivery" you're referring to just the hose connecting the petcock to the carbs that delivers the fuel (not the vacuum hose)? Just wanting to make sure I do this test correctly.
I did get a new battery last year, and that seemed to be one of the major causes of the bike to start again last year. Not sure how it's held up since, but it's seen very little use since being replaced.
Additionally, I redid the dry compression test with both spark plugs off. Results were consistent with the previous test (left = 70 psi, 70 psi; right = 72 psi, 72 psi).
I also have not formally verified that the cam timing was correct (I wasn't directly looking for it while doing my valve adjustments), but nothing looked out of the ordinary when aligning the valves to TDC.